Multiple-stage collision avoidance braking system and method

ABSTRACT

An apparatus and method for automatic actuation and control of an air braking system on a commercial vehicle, under a warning of collision conditions, has multiple stages of operation, which supplements the normal brake pedal activation and control of the air brake operation under the driver&#39;s foot control. Automatic actuation has two stages: (1) impending collision automatic activation and control for 1.4 second closure; and (2) imminent collision automatic activation and control for 0.9 seconds closure. A determination of closure occurring in excess of 1.6 seconds, turns off the warning, and also deactivates the automatic activation and control. A modification to a standard air brake system structure enables the addition of the automatic activation and control stages. When an impending collision signal is received, an activation component operates valves to pressurize the rear brakes to 40 psi. When the air pressure at the rear brakes rises to 20 psi, other valves pressurize the front brakes. This first stage automatic operation stops or slows the vehicle with 40 psi on the rear brakes and 20 psi on the front brakes. When an imminent collision signal is received, the activation component opens valves to pressurize the rear brakes to 120 psi. Once the air pressure at the rear brakes rises to 20 psi, the front brakes are also pressurized. This second stage automatic operation stops the vehicle with 120 psi on the rear brakes and 80 psi on the front brakes, unless restricted to a lower pressure by the brake system manufacturer. The driver can deactivate the automatic braking functions by stepping on the brake pedal or by operating the vehicle turn signals.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of co-pending U.S. application Ser.No. 15/439,261, filed Feb. 22, 2017, the disclosure of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION

Various types of apparatus have been introduced into the marketplace toprovide collision avoidance operation of motor vehicles, principally forcollision avoidance of automobiles and light trucks. Most of thesesystems have been specifically designed for automobiles and light truckswhich use hydraulic brake systems. In a hydraulic brake system, brakefluid is used to transmit a hydraulic pressure from the driver's pedalto the foundation brakes, with or without vacuum assistance to increasethe pressure. Braking force is dependent to a large measure upon thepressure developed by pressing the brake pedal.

Included in such collision avoidance apparatus are object detection andranging systems using radar, laser, or optical camera ranging technologyto trigger an alarm to the driver, or to adjust the setting of automaticcruise control, or to activate an automated braking system structure.

These systems serve to reduce or eliminate the effect of human reactiontime in the presence of a collision threat. They are generally intendedfor OEM, factory installation.

Present day collision alarm and avoidance systems usually take the formof a warning system or a supplemental brake control system which ismicroprocessor driven. Some of these systems prematurely control brakelight illumination of a proceeding vehicle, as a distance closurewarning to a following vehicle, before the brake pedal of the precedingvehicle is operated. Other systems calculate collision mitigation basedupon radar, yaw rate, wheel speed, and rear view camera inputs tocontrol power brake booster performance to adjust braking force in ahydraulic system. Many of these systems have electronic controllerswhich calculate velocity profiles, collision probabilities and providesupplemental brake system instructions.

Braking systems for heavy commercial highway vehicles, such as tractortrailers, heavy straight trucks, and buses, depart from the hydraulicautomobile and light truck braking systems, as they are almostexclusively air brake systems. Air brakes can develop a greater stoppingforce, use simpler components, remain operable even in the presence of aleak, and are generally more safe than hydraulic brakes. Air brakes arefound on commercial vehicles with a maximum gross vehicle weight rating(GVWR) of 33,000 pounds or more. They are also often found on vehicleswith lesser GVWR, such as 20,000 pounds.

Commercial vehicle air brake systems operate with air pressure from airreservoirs containing a volume of high pressure air, ranging from 60 psito 120 psi (maximum allowed by D.O.T.), depending upon the design of thebraking system. Typically, air reservoirs used in air brake systems areunder a pressure of 60-120 psi. There generally is a front circuit tooperate the front brakes and a rear circuit to operate the rear brakes.Each circuit has its own air reservoir.

Fail safe air brake systems provide a lesser pressure to service (work)brakes from a second air reservoir in the presence of a failure in theprimary service brake circuit. Other systems utilize a lower pressurecircuit to control the relay valves of a higher pressure service brakecircuit.

Factory available adaptive cruise control systems can electronically seta braking pressure in an air brake system above the default brakingpressure, as software resident in the system senses and calculatesvehicle factors including speed, yaw rate, lateral acceleration steeringangle and traction in regards to predetermined limits for any of thesevehicle factors. If the limits are not exceeded, a pressure above thedefault braking pressure is applied. This process is successivelyconducted and the pressure is successively increased, based on thesuccessive monitoring and calculating of values in comparison to thepredetermined factor limits, until a vehicle deceleration rate of about2 meters per second is achieved, if possible. Further pressure increasesare terminated before the target deceleration rate is achieved if anylimit is exceeded.

Very high pressure systems have been proposed for disk brake airsystems. However, this technology cannot be operatively applied topresent air brake circuits, and it is not yet approved by D.O.T.

In the past, dual pressure air brake systems have been proposed where ahigher pressure (120 psi) is generated by an on-board air compressor andstored in a first tank to operate a spring air brake circuit. Airpressure at 120 psi is passed through a pressure reducing valve to bestored at a lower pressure (60 psi) to operate a service air brakecircuit. This technology has no application to collision avoidancecircuits.

As discussed above, existing collision avoidance systems that have beendesigned for hydraulic brake systems, are not applicable (transportable)to air brake systems as air brake system components and hydraulic brakesystem components differ remarkably. The hydraulic system technology isnot transportable into air brake system technology. Moreover, existingcollision avoidance systems have not been designed for aftermarketinstallation in older vehicles. Additionally, they have not beendesigned to operate with various third party warning or detectiondevices.

The National Highway Traffic Safety Administration (NHTSA) and theInsurance Institute for Highway Safety announced in March 2016, that by2022, 99% of the new automobiles must have automatic emergency brakingsystems as a standard feature. Automatic emergency braking systems willsimilarly, also, soon be required for tractor trailers, and heavystraight trucks and buses.

The features of aftermarket installation and compatibility with existingthird party warning and detection devices are important.

It is also important to be able to modify the existing air brake systemson tractor trailers, heavy straight trucks and buses, as these vehicleshave long service lives, often extending beyond twenty years or more.These vehicle air brake systems should be able to be modified to meetthe new NHTSA standards without replacing the entire air system.

It is desirable that the modifications to existing non-electronic airbrake systems also be non-electronic, thereby eliminating or minimizingthe need for sensitive electronic components.

It is further desirable that the modified system be able to operate withdrive brake pedal air operation as originally installed.

It is also desirable that the system be able to operate with anautomatic braking method responsive to an “impending” collision(critical) situation signal, and with an automatic braking methodresponsive to an “imminent” collision (more critical) situation signal(stage 3).

It is highly desirable that the modifications of the original air brakesystem, resident in the present invention, leaves the systempneumatically activated and controlled.

SUMMARY OF THE INVENTION

An automatic braking control system and method are provided forcontrolling the automatic operation of an air brake system on acommercial highway vehicle. The system permits the normal manualoperation of the air brakes by the driver's brake pedal, under normalconditions. When a possible collision is detected, the systemautomatically operates the vehicle's air braking system to avoid ormitigate the collision. The automatic braking system is pneumaticallyoperated and controlled.

The vehicle's factory installed air braking system, in a normalconfiguration, is employed to stop the vehicle, such as tractor trailer,a heavy straight truck, or a bus, under the foot-operated brake pedalcontrol of the driver. A commercially available collision warning deviceis used to detect and calculate an impending collision and/or animminent collision, whereby the “impending” collision is determined tooccur within 1.4 seconds and the “imminent” collision is determined tooccur within 0.9 seconds.

Where the impending collision automatic braking operation does not stopthe vehicle, a second stage operation, i.e., automatic braking for animminent collision is activated. It is anticipated that the second stageoperation will either stop the vehicle or mitigate collision damage.Once the warning device determines a 1.6 second spacing, the collisionsituation is ended, the automatic activation control ceases, the excessair pressure is bled from the system, and control of the braking isreturned entirely to the driver.

The commercial collision warning device constantly calculates “closuretime”, based upon the speed of the vehicle with collision avoidance, theforegoing (preceding) vehicle's speed, and the distance between them.

The collision warning device is available from such manufacturers asWABCO Holdings, Inc., and Delphi Automotive, Inc. It is aradar-operated, ranging and closure calculating device which is adjustedto generate both the impending collision signal and an imminentcollision signal as conditions dictate.

The driver is always in control of the braking system and can deactivatethe automatic braking function by stepping on the brake pedal or byoperating the vehicle turn signals. The commercial collision warningsystem monitors for and reacts to a change of the driver's brake pedalposition. It also monitors for and reacts to the operation of thevehicle turn signals.

The invention provides a modification to a standard air brake systemstructure, which enables additional automatic activation and controlstages. This permits an after-market up-grade of the factory air brakesystem. For the air brake system on a tractor trailer, an actuationapparatus is connected to a commercial collision warning device havingsignal nodes mounted on the front of the vehicle. This activationapparatus can be a commercially available, solenoid operated, doubleacting, two position, four way, valve pair. This element can be anIngersoll Rand model A 312 SD solenoid operated valve which gets itspower from a connection to the collision warning device.

The solenoid in the activation apparatus element receives its power fromthe commercial collision warning device. When the commercial collisionwarning device detects a change in driver brake pedal position or theactivation of the vehicle turn signals, it shuts-off power to theactivation apparatus and deactivates the automatic braking operation.

The connection between the collision warning device and the actuationapparatus is hard wired. This is the only non-pneumatic connection inthe invention's activation apparatus. The activation apparatus haspneumatic control lines output therefrom. Air pressure is supplied tothe actuation apparatus from an air reservoir at its existing pressure,i.e., at 120 psi.

A first pneumatic output from this actuation apparatus is connected tooperate a delayed application air control connection element positionedin the air pressure line between the front brake control valve and theair control connection for the front brake actuators. A second pneumaticoutput from the actuation apparatus is connected to operate an immediateapplication control connection element positioned in the air pressureline between the rear brake control valve and a rear brake relay valvewhich leads to the rear brake actuators of a tractor and a trailer brakeactuators, if a trailer is present.

Thus, the system uses high pressure air, at 120 psi, to control thestate of certain valves which provide the service air pressure tooperate the rear and front service brakes. In controlling the airpressure to the vehicle's service brakes, the loss of control of thevehicle's travel path during panic stopping is minimized. Air pressureis always first applied to the rear service brakes, before it is appliedto the front service brakes. Air pressure is applied to the front brakesonly after (when) a threshold pressure value has been achieved on therear brakes. Moreover the service air pressure to the rear and frontbrakes is always controlled so that the rear pressure is always higherthan the front pressure. The rear pressure is significantly higher thanthe front pressure. This assures that the rear brakes are alwaysphysically engage before the front brakes and the rear brake stoppingforce is greater than at the front brakes. This eliminates or minimizesthe possibility of a jackknife, or side skidding of the rear of thevehicle.

The activation apparatus, a dual operation solenoid valve pair receivesair pressure from an air pressure reservoir to be selectively passedinto the invention piping in response to signals from the collisionwarning device. The activation apparatus is normally closed, andprovides air pressure at a first output when an impending collisionsignal is present, and air pressure at second output when an imminentcollision signal is present. Only one output of the activation apparatuscan be active at a time.

When an impending collision signal is received indicating a collision inapproximately 1.4 seconds, the activation apparatus component controlsvalves opening to pressurize the rear foundation brakes to 40 psi, withair from a rear air reservoir. When the air pressure at the rear brakesrises to 20 psi, other valves are controlled to pressurize the frontbrakes with air from a front air reservoir. This automatic operationstops or slows the vehicle with 40 psi on the rear brakes and 20 psi onthe front brakes.

When an imminent collision signal is received indicating a collision inapproximately 0.9 seconds, the activation component enables valves toopen to pressurize the rear brakes to 120 psi with air from the rear airreservoir. When the air pressure at the rear brakes rises to 20 psi, thefront brakes are pressurized with air from the front air reservoir. Thisautomatic operation stops the vehicle with 120 psi on the rear brakesand 80 psi on the front brakes, unless restricted to a lower pressure bythe brake system manufacturer. For example some air brake equipment canonly tolerate lower pressures, such as 80 psi on the rear circuit and 60psi on the front circuit.

By having this braking sequence of the rear service brakes and the frontservice brakes, the rear tires always want to stop faster than the fronttires. This eliminates or minimizes the tendency to fishtail, jackknifeor the vehicle rolling over.

The present invention provides a modification to a standard air brakesystem structure, which enables the additional automatic activation andcontrol stages. In the presence of an impending collision signal (1.4seconds closure) the activation component opens valves to pressurize therear service brakes are pressurized to about 40 psi, with air from arear air reservoir. When the air pressure at the rear brakes rises toabout 20 psi, other valves are opened to pressurize the front brakeswith air from a front air reservoir. This automatic operation stops orslows the vehicle with about 40 psi on the rear brakes and about 20 psion the front brakes. In the presence of an imminent collision signal(0.9 seconds closure), the activation component enables valves to opento pressurize the rear brakes to about 120 psi with air from the rearair reservoir. When the air pressure at the rear brakes rises to about20 psi, the front brakes are pressurized with air from the front airreservoir to about 20 psi. Thus, this automatic operation stops thevehicle with about 120 psi on the rear brakes and about 80 psi on thefront brakes.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be understood from a reading of the followingdescription and the attached claims, in connection with the accompanyingdrawings, in which like numerals refer to like elements and in which:

FIG. 1 is a block diagram for the invention system;

FIG. 2 shows the braking distance curve for an air brake systemoperating normally, with manual brake actuation from brake pedaloperation;

FIG. 3 shows the braking distance curve with automatic brake actuationof the present invention; and

FIG. 4 shows the braking distance curve of the invention when coupledwith an optional electromagnetic retarder on the drive shaft or on arear axle.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is a pneumatically operated and pneumaticallycontrolled automatic braking control system and method for controllingair brakes on a commercial highway vehicle. The system operates inmultiple stages. There is normal manual operation of the air brakes bythe driver's brake pedal under normal conditions. When a possiblecollision is detected, the system automatically operates the vehicle'sair braking system, by first applying air pressure to the rear brakes.When the pressure at the rear brakes has reached 20 psi, air pressure isapplied to the front brakes. The air pressure applied on the rear brakesis ultimately 40 psi, and on the front brakes is ultimately 20 psi.

In a next stage, air pressure is also first applied to the rear brakes.When the rear brake pressure reaches 20 psi, air pressure is fed to thefront brakes. In this stage, the air pressure on the rear brakes isultimately 120 psi and on the front brakes is 80 psi. These pressuresare reduced when required by the manufacturer's specifications.

The initial stage is activated when the vehicle is calculated to beapproximately 1.4 seconds from impact. The next stage is activated whenthe vehicle is calculated to be approximately 0.9 seconds from impact.

FIG. 1 shows a block diagram of the structure of the invention. In adriver operated mode, a driver operated brake pedal 21 operates a rearbrakes control valve 23 and a front brakes control valve 25,concurrently. The rear brake control valve 23 receives air pressure froma rear air reservoir 45 via a pneumatic line 44. The front brake controlvalve 25 receives air pressure from a front air reservoir 29 via apneumatic line 31.

The output from the rear brake control valve 23 is connected to a rearservice brake relay valve 51 via pneumatic line 52. Rear relay valve 51then passes air pressure onto a left and a right rear ABS module 55, 57via pneumatic line 53. The left and right rear ABS modules 55, 57respectively feed left and right tandem brake actuators 59, 61.

The rear relay valve 51 via an additional pneumatic line 70 passes airpressure through a tractor protection valve 75 to a trailer servicebrake line 77, if a trailer is present.

The output from the front brake control valve 25 is connected to a front“T” connector gate 36 though a pneumatic line 81. Front connector gate36 passes air pressure to a left and a right ABS module 37, 39 via apneumatic line 40. Left and right ABS modules 37, 39 feed air pressureto left and right front brake actuators 41, 43, respectively.

A commercial warning device 11 is employed to detect collisionconditions and to send signals indicating one or the other of twocollision conditions, “impending” or “imminent”. The output from thewarning device 11 is three electrical wires 15, a “high” signal, a “low”signal and a ground. The low signal indicates an impending collision.The high signal indicates an imminent collision. No signal indicates anon-collision situation. Electrical connection cabling 15 powers (i.e.,drives) an actuation apparatus 13, which actuator is an electronic, twostage, solenoid operated, air valve. The actuation apparatus 11 has twooutputs. The first output is connected to a pneumatic line 19, while thesecond output is connected to a pneumatic line 79.

An “impending” collision (i.e., closure) indicates a collision in 1.4seconds. An “imminent” collision indicates a collision (i.e., closure)indicates a collision in 0.90 seconds. A closure equal to or greaterthan 1.6 seconds is a non-collision condition.

The air pressure in the front air reservoir 29 is about 120 psi. The airpressure in the rear air reservoir is also kept at about 120 psi.Pneumatic line 49 feeds the 120 psi pressure to the actuation apparatus11, which in turn feeds a one-way connector gate 71, via the pneumaticline 19. A pneumatic line 85 exits the one-way gate 71 and connects to apressure regulator, step down gate 69. Regulator gate 69 can beadjustable. Regardless, it reduces the 120 psi from the actuationapparatus 11 to a pressure of 40 psi. The output of regulator gate 69 isconnected to a connection “T” gate 83. An output line 84 from gate 83 isconnected into a crack valve 36. The output of the crack valve 35 isconnected into the front “T” connector gate 36 to ultimately lead to thefront brake actuators 37, 39. The crack valve 35 operation may beadjustable. The crack valve 35 of the present invention is set toquickly release (open) at 20 psi.

Another pneumatic line from the “T” connection gate 83 is connected intoa “T” connection gate 73. A pneumatic line from gate 73 connects to aconnector “T” gate 65 via a pneumatic line 72. The gate 73 is alsoconnected to an output from the rear brake control valve 23. The secondoutput from the actuation device 11 via a pneumatic line 79 connectswith the connector gate 79 which is connected to the input 67 of therear relay valve 51 via a pneumatic line 63.

Air pressure is output from the actuation apparatus 11 via line 19 in an“impending” collision condition, i.e., where there is about 1.4 secondsof closure time until impact. In this situation there is no air pressureon line 79 from the other output actuator 11.

Air pressure is output from the actuation apparatus 11 via line 79 in an“imminent” collision condition, i.e., where there is about 0.9 secondsof closure time until impact. In this situation there is no air pressureon line 19 from the other output from actuator 11.

As an option, an electro-magnetic retarder device may be added, to bemounted to a rear axle or to the drive shaft to contribute additionalbraking action. Such retarders are frictionless stopping aids which areused to slow vehicles to prevent the service brakes from overheating andto minimize stopping distance. Retarders are commercially available fromsuch manufacturers as Frenelsa S. A., Telma, S. A., Cama Products,Kimbo/Sharp Corporation and others.

When 1.4 seconds to impact is detected, the invention sends air pressurefrom rear reservoir 45 through the actuator 11, FIG. 1. Then via line 19though gate 71, via line 85, through gate 69, through regulator 69,though gate 83, and via line 84 to wait for crack valve 35.

Air pressure also flows though gate 83, through gate 73, via line 72 togate 65, and there through. The air pressure travels via line 63 toinput 67 and through relay gate 51 to the rear brakes. The other outputfrom actuator 11 is closed.

When the pressure at the rear brakes relay valve 51 rises to 20 psi,there is also 20 psi at the crack valve 35. Crack valve 35 then opensand air pressure begins to build on the front brakes as it continues toincrease on the rear brakes. The rear brake pressure is higher than thefront brake pressure and remains so. The pressure is held with 40 psi onthe rear brakes and 20 psi on the front brakes to stop the vehicle. Whena trailer is present, trailer brake pressure will approximate the rearbrake pressure at 40 psi.

When 0.9 seconds to impact is detected, the invention send air pressurefrom rear reservoir 45 through the actuator 11, and then via line 79 tothe gate 65. The other output port from actuator 11 is closed.

The pressure at gate 65 is sent via line 63 to the rear relay valve 51and via line 72 to gate 73. From gate 73 the pressure passes through thegate 83 and then via line 84 to the crack valve. When the pressure atthe crack valve rises to 20 psi the crack valve opens and pressurebegins to build on the front brakes, while continuing to rise on therear brakes. The rear brake pressure is higher that the front brakepressure and remains so. A pressure of 120 psi is held on the rearbrakes and 80-100 psi on the front brakes to stop or slow the vehicle.Again, when a trailer is present, the trail brake pressure will followthe rear brake pressure at 120 psi.

The operation of the invention, including following distance, responsetime and vehicle speed, is shown in FIG. 3, and can be compared with thesame factors for the operation of a manual braking system, FIG. 2, andthe same factors for the operation of the invention coupled with acommercial electro-magnetic retarder mounted to the vehicle drive shaft,or rear axle. These graphs were generated from test results obtained byoperating the same test vehicle, which was first-operated with manualbraking, then, secondly, with the collision avoidance braking inventionin place, and lastly, with a drive shaft mounted retarder or rear axlemounted retarder added to the invention.

In each of these graphs (FIGS. 2, 3, 4) the solid line 87 shows vehiclefollowing distance. Each of the graphs show a closure, i.e., a reductionin following distance of the test vehicle with respect to a precedingvehicle. For the manual system, FIG. 2, the response time, once acollision warning is generated, is shown as time of driver collisionrecognition 91, driver response 93, and brake response 95. For thepresent invention, FIG. 3, the response time once a warning isgenerated, is indicated by brake response 95 followed by brakedeceleration 97. It is important to note that brake deceleration 97 isshown to occur much sooner in FIGS. 4 and 5, than in FIG. 3.

The next important factor to note is the time of closest vehicleapproach 99. This is the demarcation point, where the test vehiclebraking action results in an increase in the distance to the foregoingvehicle, thereby avoiding a collision. This factor relates to the speedcurve 101 of the braking vehicle which shows a reduction in speed 101,FIGS. 2, 3, 4, during braking. This speed reduction is seen to occursoonest in FIG. 4. The time to speed reduction is seen to be slightlyless in FIG. 3. FIG. 2 shows the largest delay before a speed reductionoccurs.

Once braking has occurred, the driver must make an evaluation 103. Thedriver controls the acceleration 105 of the vehicle 105 if conditionswarrant. Once a safe distance is achieved 107, driver acceleration isended 109.

With manual braking, FIG. 2, the warning duration 111 extends from thestart of the warning signal 89 to the time a safe distance is achieved107. With the invention, FIG. 3, the warning duration 111, is less, asit extends from the start of the warning signal 89 to the achievement ofa safe distance 107 at the beginning of driver evaluation 103.

With the addition of an electro-magnetic retarder, FIG. 4, warningduration 111 is further shortened and additional braking improvement 113occurs. This improvement 113 is shown as the time from the achieved safedistance 107 time, to the time almost to the termination of drivercontrolled acceleration 109.

The following elements are shown in the accompanying drawings.

-   11 collision warning device-   13 actuation apparatus—electronic, two stage, solenoid operated, air    valve-   15 electrical connection cabling—HLG (high low ground) cable wire-   19 pneumatic line from actuation apparatus 11 to gate 71-   21 driver brake pedal-   23 rear brakes control valve-   25 front brakes control valve-   29 front air reservoir-   31 pneumatic line from front air reservoir 29 to front brakes    control valve 25-   35 quick release crack valve-   36 front “T” connector gate-   37 left front ABS-   39 right front ABS-   40 pneumatic line from connector gate 36 to ABS 37 and 39-   41 left front actuator-   43 right front actuator-   44 pneumatic line from rear air reservoir to rear control valve 23-   45 rear air reservoir-   47 air supply connector-   50 pneumatic line from rear brake control valve 25 to relay valve 51-   51 service brake relay valve-   53 pneumatic output to rear ABS 55 and 57-   55 left rear ABS-   57 right rear ABS-   59 left rear brake actuator-   61 right rear brake actuator-   63 pneumatic feed from gate 65 to rear relay valve input 67-   65 connector “T” gate-   67 input for rear relay valve 51-   69 pressure regulator step down gate 120 psi to 40 psi-   70 pneumatic line from rear relay valve to tractor protection valve    75-   71 one-way connector gate-   72 pneumatic line from gate 73 to gate 65-   73 pneumatic “T” connection gate between gate 83 and rear control    valve 23-   75 tractor protection valve-   77 trailer service brake line-   79 pneumatic line from activation apparatus 11 to connector gate 65-   81 pneumatic line from front brake control valve 25 to front “T”    connector gate 36, which-   connector gate also is connected to the output from crack valve 35-   83 pneumatic connection “T” gate from pressure reducer 69-   84 pneumatic line from gate 83 to crack valve 35-   85 pneumatic line from one-way gate 71 to pressure reducer 69-   87 solid line following distance-   89 collision warning-   91 driver recognition-   93 driver response-   95 brake response-   97 brake deceleration-   99 time of closest approach-   101 speed curve-   103 driver evaluation-   105 driver acceleration-   107 safe distance achieved-   109 acceleration ended-   111 warning duration-   113 improvement in braking

The foregoing description is intended to be illustrative of theinvention. Modifications and substitutions may be introduced withoutdeparting from the scope or intent of the described invention or theaccompanying claims.

What is claimed:
 1. A method of automatic braking, collision avoidancefor vehicle air brake systems, including the steps of: detecting animpending collision condition; pressurizing the rear brakes with asource pressure of about 40 psi when said impending collision conditionis detected; pressurizing the front brakes when the pressure at the rearbrakes has risen to about 20 psi; and maintaining an air pressure of 40psi at the rear brakes and 20 psi at the front brakes to slow or stopthe vehicle.
 2. The method of collision avoidance of claim 1, includingthe steps of: detecting an imminent collision condition; pressurizingthe rear brakes with a source pressure of about 120 psi when saidimminent collision condition is detected; begin pressurizing the frontbrakes when the pressure at the rear brakes has risen to about 20 psi;and maintaining an air pressure of about 120 psi at the rear brakes andabout 80 psi at the front brakes to slow or stop the vehicle.
 3. Themethod of collision avoidance of claim 1, including the steps of:detecting an imminent collision condition; pressurizing the rear brakesto a pressure of about 80 psi when said imminent collision condition isdetected; begin pressurizing the front brakes when the pressure at therear brakes has risen to about 20 psi; and maintaining an air pressureof about 80 psi at the rear brakes and about 60 psi at the front brakesto slow or stop the vehicle.
 4. The method of collision avoidance ofclaim 1, including releasing said brake pressure and returning brakeoperation entirely to the driver when a non-collision condition isdetected.
 5. The method of collision avoidance of claim 1, wherein saidimpending collision is determined to occur in about 1.4 seconds.
 6. Themethod of collision avoidance of claim 2, wherein said imminentcollision is determined to occur in about 0.9 seconds.
 7. The method ofcollision avoidance of claim 4, wherein said non-collision condition isdetermined by a closure of greater than 1.6 seconds.
 8. The method ofcollision avoidance of claim 1, including maintaining a front airpressure reservoir at 120 psi, and a rear air pressure reservoir at 120psi, and pressurizing said rear brakes from said rear reservoir, andpressurizing said front brakes from said front reservoir.
 9. The methodof collision avoidance of claim 2, including maintaining a front airpressure reservoir at 120 psi, and a rear air pressure reservoir at 120psi, wherein said pressurizing of said rear brakes is from said rearreservoir, and said pressurizing of said front brakes is from said frontreservoir.
 10. The method of collision avoidance of claim 8, wherein thestep of pressurizing the rear brakes includes opening at least one valvebetween said rear air pressure reservoir and said rear service brakeswith an air control pressure of 120 psi, and opening at least one valvebetween said front air pressure reservoir and said front service brakeswith an air control pressure of 120 psi.
 11. The method of collisionavoidance of claim 8, wherein the step of pressurizing the rear brakesincludes opening at least one valve between said rear air pressurereservoir and said rear service brakes with an air control pressure of120 psi, and opening at least one valve between said front air pressurereservoir and said front service brakes with an air control pressure of120 psi.
 12. An automatic braking collision avoidance system, for acommercial vehicle air brake system, having a front brake circuit and arear brake circuit, comprising: a collision warning device providing asignal representing closure time with a foregoing vehicle or object,including an impending collision warning signal and an imminentcollision warning signal; a rear air pressure reservoir, and a front airpressure reservoir, where the pressure in said rear and front reservoirsis each maintained at the same pressure; an actuation apparatus elementbeing electrically connected to said collision warning device forreacting to an impending collision warning signal and to an imminentcollision warning signal; at least one connection element in a pneumaticpressure line between said rear air pressure reservoir and said rearservice brake circuit, wherein said connection element operates as avalve; at least one connection element in a pneumatic pressure linebetween said front air pressure reservoir and said front service brakecircuit, wherein said connection element operates as a valve; whereinwhen an impending collision warning signal is detected, said actuationapparatus first controls said rear air service brake pressure topressurize said rear brake circuit such that when said rear brakepressure reaches a first threshold, said actuation apparatus controlssaid front air service brake pressure to pressurize said front brakes;wherein when the pressure at said rear brakes and the pressure at saidfront brakes each reach its predetermined target pressure, furtherpressure increases are ceased and the target pressures are maintained.13. The automatic braking collision avoidance system of claim 12,wherein when an imminent collision warning signal is detected, saidactuation apparatus first controls said rear air service brake pressureto pressurize said rear brake circuit at a target pressure of said rearair reservoir pressure, wherein when said rear brake pressure reaches afirst threshold, said actuation apparatus controls said front airservice brake pressure to pressurize said front brakes to a targetpressure of less than said rear brake target pressure, wherein when saidrear brake pressure and said front brake pressure each reach thepredetermined ultimate target pressures, further air pressure increasesare ceased, and the ultimate target pressures are maintained.
 14. Theautomatic braking collision avoidance system of claim 12, wherein thefirst threshold pressure at said rear brakes is about 20 psi, andwherein the predetermined target pressure at which said air pressureincreases are ceased is at about 40 psi for said rear brakes, and atabout 20 psi for said front brakes.
 15. The automatic braking collisionavoidance system of claim 13, wherein said rear air pressure reservoirand said front air pressure reservoir are each at about 120 psi, andwherein the rear brake pressure threshold for activating said frontbrake pressure is about 20 psi, and wherein the predetermined ultimatetarget pressure at said rear brake circuit is 120 psi and at said frontbrake circuit is about 80 psi.
 16. The automatic braking collisionavoidance system of claim 12 wherein said valve action between said rearair pressure reservoir and said rear service brake circuit is controlledwith a high pressure pneumatic signal from said actuation apparatus,which pneumatic control signal passes through a delayed operation gatepneumatically connected to a rear brake control valve, the operation ofsaid delayed operation gate being controlled by a separate pneumaticcontrol signal form said actuation apparatus.
 17. The automatic brakingcollision avoidance system of claim 12 wherein said actuation apparatuselement is an electronic solenoid operated two stage valve.
 18. Theautomatic braking collision avoidance system of claim 13, wherein saidactuation apparatus element is an electronic solenoid operated two stagevalve.
 19. The automatic braking collision avoidance system of claim 18,also including a quick release crack valve connected to the frontbrakes, a front brake control valve pneumatically powering said crackvalve.
 20. A method of automatic braking, collision avoidance forvehicle air brake systems, including the steps of: receiving a collisionindication signal; pressurizing the rear brakes with a first higherpressure when said collision indication signal is detected; pressurizingthe front brakes when the pressure at the rear brakes has risen to afirst threshold value which is less than said first higher pressure,said pressurizing maintaining a pressure differential between a higherrear brake pressure and a lower front brake pressure; and maintaining anhigher air pressure of at the rear brakes and a lower air pressure atthe front brakes at said pressure differential, to slow or stop thevehicle.